ASCE 7 AND THE DEVELOPMENT OF A TSUNAMI BUILDING CODE FOR THE U.S.

ASCE 7 AND THE DEVELOPMENT OF A TSUNAMI BUILDING CODE FOR THE U.S.

Gary Chock, ASCE 7 TLESC ChairGary Chock, ASCE 7 TLESC Chair

Tohoku Tsunami photograph at Minami Soma by Sadatsugu Tomizawa

Background Information on the Objective of the ASCE TLESCBackground Information on the Objective of the ASCE TLESC

A  national standard for engineering design for tsunami effects written in mandatory language does not exist.  As a result, tsunami risk to coastal zone construction is not explicitly and comprehensively addressed in design.

The Tsunami Loads and Effects Subcommittee of the ASCE/SEI 7  Standards Committee is developing a proposed new Chapter 6 ‐Tsunami Loads and Effects for the ASCE 7‐16 Standard.  

Anticipated completion  by TLESC in November 2013 Review by ASCE 7 Main Committee in 2014 ASCE 7‐16 to be published by March 2016 ASCE 7 Tsunami Provisions will then be referenced in IBC 2018 Local jurisdiction codes could decide to adopt Chapter 6 earlier.

A  national standard for engineering design for tsunami effects written in mandatory language does not exist.  As a result, tsunami risk to coastal zone construction is not explicitly and comprehensively addressed in design.

The Tsunami Loads and Effects Subcommittee of the ASCE/SEI 7  Standards Committee is developing a proposed new Chapter 6 ‐Tsunami Loads and Effects for the ASCE 7‐16 Standard.  

Anticipated completion  by TLESC in November 2013 Review by ASCE 7 Main Committee in 2014 ASCE 7‐16 to be published by March 2016 ASCE 7 Tsunami Provisions will then be referenced in IBC 2018 Local jurisdiction codes could decide to adopt Chapter 6 earlier.

ASCE 7-16ASCE 7-16

Minimum Design Loads for Buildings and Other Structures Chap 1 & 2 – General and load combinations Chap 3 - Dead, soil and hydrostatic loads Chap 4 - Live loads Chap 5 - Flood loads (riverine and storm surge) Chap 6 – Tsunami loads and effects Chap 7 - Snow loads Chap 8 - Rain loads Chap 10 - Ice loads Chap 11 – 23 - Seismic Design Chap 26 – 31 - Wind Loads

Minimum Design Loads for Buildings and Other Structures Chap 1 & 2 – General and load combinations Chap 3 - Dead, soil and hydrostatic loads Chap 4 - Live loads Chap 5 - Flood loads (riverine and storm surge) Chap 6 – Tsunami loads and effects Chap 7 - Snow loads Chap 8 - Rain loads Chap 10 - Ice loads Chap 11 – 23 - Seismic Design Chap 26 – 31 - Wind Loads

USA Codes and StandardsUSA Codes and Standards

Other Standards: Material specific

design specifications Non-structural

installation standards Testing and

qualification standards

Other Standards: Material specific

design specifications Non-structural

installation standards Testing and

qualification standards

• International Building Code (IBC)• ASCE 7 Minimum Design Loads for Buildings and Other Structures (ASCE 7) developed in an ANSI‐accredited consensus process

Post-Disaster Observations

Design and Construction Practice

The Code Development ProcessThe Code Development Process

Research & Development

Codes and Standards

Experience from Design Practice and

Post-Disaster Surveys

Special Considerations for Tsunami DesignSpecial Considerations for Tsunami Design

For Pacific NW regions governed by nearby offshore earthquakes, structure will need to resist earthquake prior to onset of tsunami.

Need for local tsunami inundation mapping of hydrodynamic loading parameters, based on probabilistic regional offshore tsunami heights

Tsunami wave height not proportional to EQ magnitude Include possible earthquake-induced subsidence affecting tsunami

inundation Flow acceleration in urban landscapes Analyze the key loading phases of depth and velocity in momentum

flux pairs Tsunami forces not proportional to building mass Inflow and outflow characteristics will be different Debris accumulation and low-speed debris impacts Scour depth at the perimeter of the building can be equal to the flow

depth

For Pacific NW regions governed by nearby offshore earthquakes, structure will need to resist earthquake prior to onset of tsunami.

Need for local tsunami inundation mapping of hydrodynamic loading parameters, based on probabilistic regional offshore tsunami heights

Tsunami wave height not proportional to EQ magnitude Include possible earthquake-induced subsidence affecting tsunami

inundation Flow acceleration in urban landscapes Analyze the key loading phases of depth and velocity in momentum

flux pairs Tsunami forces not proportional to building mass Inflow and outflow characteristics will be different Debris accumulation and low-speed debris impacts Scour depth at the perimeter of the building can be equal to the flow

depth

6.1   General Requirements6.2   Definitions6.3   Symbols and Notation 6.4   Tsunami Risk Category Design Criteria6.5  Procedures for Determination of Offshore Tsunami Wave Height6.6  Procedures for Determining Tsunami Inundation 6.7  Design Parameters for Tsunami Flow over Land6.8   Structural Design Procedure for Tsunami Effects6.9   Hydrostatic Loads6.10   Hydrodynamic Loads6.11  Impact Loads6.12  Foundation Design6.13  Structural countermeasures for reduced loading on buildings6.14  Special Occupancy Structures 6.15  Designated Nonstructural Systems (Stairs, Life Safety MEP)6.16  Non‐building critical facility structuresC6   Commentary and References

6.1   General Requirements6.2   Definitions6.3   Symbols and Notation 6.4   Tsunami Risk Category Design Criteria6.5  Procedures for Determination of Offshore Tsunami Wave Height6.6  Procedures for Determining Tsunami Inundation 6.7  Design Parameters for Tsunami Flow over Land6.8   Structural Design Procedure for Tsunami Effects6.9   Hydrostatic Loads6.10   Hydrodynamic Loads6.11  Impact Loads6.12  Foundation Design6.13  Structural countermeasures for reduced loading on buildings6.14  Special Occupancy Structures 6.15  Designated Nonstructural Systems (Stairs, Life Safety MEP)6.16  Non‐building critical facility structuresC6   Commentary and References

Proposed Scope of the ASCE Tsunami Design Provisions2016 edition of the ASCE 7 Standard, Minimum Design Loads

for Buildings and Other Structures

Proposed Scope of the ASCE Tsunami Design Provisions2016 edition of the ASCE 7 Standard, Minimum Design Loads

for Buildings and Other Structures

Risk categories of buildings and other structures per ASCE 7

Risk categories of buildings and other structures per ASCE 7

Risk Category I Buildings and other structures that represent a low risk tohumans

Risk Category II All buildings and other structures except those listed inRisk Categories I, III, IV

Risk Category III Buildings and other structures with potential to cause asubstantial economic impact and/or mass disruption ofday-to-day civilian life in the event of failure.

Risk Category IV Buildings and other structures designated as essentialfacilities

• Evacuation procedures for emergency response are still necessary.• In most communities, it will not be economically practical or justified to

prohibit construction in a tsunami hazard zone based on a long return period. Therefore, the tsunami maps of ASCE are not for land use zoning

Tsunami Risk Category Design Criteria

Tsunami Risk Category Design Criteria

Not applicable to any buildings within the scope of the International Residential Code; Not applicable to light-frame residential construction

Not applicable to any Risk Category I buildings Not applicable to any Risk Category II structures up to

~65 feet in height Applicable to all Risk Category III and IV buildings and

structures, and Risk Category II buildings greater than 65 ft height for reliable life safety and reasonable economy

Economic impact in high seismic regions is anticipated to be nominal since most buildings subject to these requirements will be designed to Seismic Design Category D or greater (design for inelastic ductility).

Not applicable to any buildings within the scope of the International Residential Code; Not applicable to light-frame residential construction

Not applicable to any Risk Category I buildings Not applicable to any Risk Category II structures up to

~65 feet in height Applicable to all Risk Category III and IV buildings and

structures, and Risk Category II buildings greater than 65 ft height for reliable life safety and reasonable economy

Economic impact in high seismic regions is anticipated to be nominal since most buildings subject to these requirements will be designed to Seismic Design Category D or greater (design for inelastic ductility).

Structural Performance LevelsStructural Performance Levels

IMMEDIATE OCCUPANCY STRUCTURAL PERFORMANCE: The post-event damage state in which a structure remains safe to occupy

LIFE SAFE STRUCTURAL PERFORMANCE: The post-event damage state is that in which a structure has damaged components but retains a margin against onset of partial or total collapse.

COLLAPSE PREVENTION STRUCTURAL PERFORMANCE: The post-event damage state is which a structure has damaged components and continues to support gravity loads but retains little or no margin against collapse.

IMMEDIATE OCCUPANCY STRUCTURAL PERFORMANCE: The post-event damage state in which a structure remains safe to occupy

LIFE SAFE STRUCTURAL PERFORMANCE: The post-event damage state is that in which a structure has damaged components but retains a margin against onset of partial or total collapse.

COLLAPSE PREVENTION STRUCTURAL PERFORMANCE: The post-event damage state is which a structure has damaged components and continues to support gravity loads but retains little or no margin against collapse.

Design based on Risk CategoryDesign based on Risk Category

Tsunami Design Performance Level

Tsunami Frequency

OperationalImmediate (Repairable) Occupancy

Life Safe Collapse Prevented 

Occasional (100 years)

Risk Category IV Risk Category III Risk Category II

Max Considered (2500 yrs)

Risk Category IV Risk Category III and > 65‐ft. high Risk Category II

This is not a table of Performances for Seismic Ground Shaking

Tsunami-genic Seismic Sources of Principal Relevance to the USA

Tsunami-genic Seismic Sources of Principal Relevance to the USA

M8.8 Maule Eq.Feb, 27, 2010

M8.0 Samoa Eq.Sept, 29, 2009

M9.0 Japan Eq.Mar, 11, 2011

Lexicon Hierarchy of Hazard Definition from an Engineering (and Code Development) PerspectiveLexicon Hierarchy of Hazard Definition from an Engineering (and Code Development) Perspective

Hypothetical Hazards Historical and Paleo Hazards Hazard Assessment Probabilistic Hazard Analysis Vulnerability and Exposure Assessment Vulnerability Analysis Engineering Risk Analysis

ASCE Tsunami Provisions to be applicable only to states and territories with quantifiable and historically significant hazard:

Alaska, Washington, Oregon, California, Hawaii, and Guam, American Samoa, and Puerto Rico

Hypothetical Hazards Historical and Paleo Hazards Hazard Assessment Probabilistic Hazard Analysis Vulnerability and Exposure Assessment Vulnerability Analysis Engineering Risk Analysis

ASCE Tsunami Provisions to be applicable only to states and territories with quantifiable and historically significant hazard:

Alaska, Washington, Oregon, California, Hawaii, and Guam, American Samoa, and Puerto Rico

Procedures for Determination of Offshore Tsunami Wave HeightProcedures for Determination of Offshore Tsunami Wave Height

Performance criteria to be based on 2,500-year hazard level Maximum Considered Tsunami for consistency with ASCE 7 seismic hazard criteria with tsunami as a coseismic effect.

A probabilistic Hazard Map of offshore tsunami height is being developed and will be incorporated in the Standard.

The tsunami hazard inland inundation limiting zone affected at the 2,500-year level would be identified.

Criteria will identify where ground shaking and subsidence from a preceeding local offshore Maximum Considered Earthquake needs to be considered prior to tsunami arrival (for Alaska and the regions directly affected by the Cascadia Subduction Zone).

Performance criteria to be based on 2,500-year hazard level Maximum Considered Tsunami for consistency with ASCE 7 seismic hazard criteria with tsunami as a coseismic effect.

A probabilistic Hazard Map of offshore tsunami height is being developed and will be incorporated in the Standard.

The tsunami hazard inland inundation limiting zone affected at the 2,500-year level would be identified.

Criteria will identify where ground shaking and subsidence from a preceeding local offshore Maximum Considered Earthquake needs to be considered prior to tsunami arrival (for Alaska and the regions directly affected by the Cascadia Subduction Zone).

Lessons from the Tohoku, Chile, and Sumatra Tsunamis

Lessons from the Tohoku, Chile, and Sumatra Tsunamis

Recorded history may not provide a good measure of the potential heights of great tsunamis.

Planning must consider the occurrence of events greater than in the historical record

Therefore, probabilistic physics-based Tsunami Hazard Analysis should be performed in addition to historical event scenarios

Recorded history may not provide a good measure of the potential heights of great tsunamis.

Planning must consider the occurrence of events greater than in the historical record

Therefore, probabilistic physics-based Tsunami Hazard Analysis should be performed in addition to historical event scenarios

Probabilistic Tsunami Hazard AnalysisProbabilistic Tsunami Hazard Analysis

• The 2,500‐year tsunami offshore wave height to used as the initial condition benchmark for local inundation maps or prescriptive inundation calculation

• The specified offshore wave height is attributed to the disaggregated predominant seismic sources for that region.

Procedures for Determining Tsunami Inundation and Design Parameters

Procedures for Determining Tsunami Inundation and Design Parameters

Site-specific modeling to give expected flow depths, velocities, and horizontal inundation limits

Site-specific modeling to give expected flow depths, velocities, and horizontal inundation limits

Structural Design Procedures for Tsunami Effects

Structural Design Procedures for Tsunami Effects

Design as an extraordinary event (with no load factor on the tsunami effect)

Consider critical stages of inundation Consider preceding earthquake if a local

subduction zone

Design as an extraordinary event (with no load factor on the tsunami effect)

Consider critical stages of inundation Consider preceding earthquake if a local

subduction zoneConceptual Illustration: In the limit, if earthquake demand exhausts ductility to the Collapse Prevention point , the available tsunami capacity would be found to the right of the seismic end state, up to the strength degraded capacity boundary

Frame of Reference for capacity space for post-earthquake tsunami resistance then becomes severely force-controlled if seismic exhausts pre-degradation cyclic load path

Structural Design Procedures for Tsunami Effects

Structural Design Procedures for Tsunami Effects

Post-Life Safety Seismic Performance and resulting available response region for Tsunami Performance

This may also define a force-controlled response space if available post-yield deformation becomes insufficient (per ASCE 41)

Post-Life Safety Seismic Performance and resulting available response region for Tsunami Performance

This may also define a force-controlled response space if available post-yield deformation becomes insufficient (per ASCE 41)

Structural Design Procedures for Tsunami Effects

Structural Design Procedures for Tsunami Effects

Post –Immediate Occupancy Seismic Performance and available response region for Tsunami Performance

Post –Immediate Occupancy Seismic Performance and available response region for Tsunami Performance

Structural Design Procedures for Tsunami Effects

Structural Design Procedures for Tsunami Effects

Available response region for Tele-Tsunami Performance

Available response region for Tele-Tsunami Performance

Tsunami Loads and EffectsTsunami Loads and Effects

Hydrostatic Forces: Unbalanced Lateral Forces Buoyant Uplift Residual Water Surcharge Loads on Elevated Floors

Hydrodynamic Forces: Lateral Impulsive Forces of Tsunami Bores Hydrodynamic Pressurization Surge Forces Damming by Waterborne Debris

Waterborne Debris Impact Forces Scour Effects:

Shear of cyclic inflow and outflow Transient liquefaction during rapid drawdown

Hydrostatic Forces: Unbalanced Lateral Forces Buoyant Uplift Residual Water Surcharge Loads on Elevated Floors

Hydrodynamic Forces: Lateral Impulsive Forces of Tsunami Bores Hydrodynamic Pressurization Surge Forces Damming by Waterborne Debris

Waterborne Debris Impact Forces Scour Effects:

Shear of cyclic inflow and outflow Transient liquefaction during rapid drawdown

Hydrodynamic Lateral Loading on Walls - Japan

Hydrodynamic Lateral Loading on Walls - Japan

Onagawa reinforced concrete fish storage buildingOnagawa reinforced concrete fish storage building

Rikuzentakata Takada Matsubara Building Shear Wall Blowout

Building Performance - Debris LoadingBuilding Performance - Debris Loading

Three-Story SMRF collapsed and pushed into concrete building

Three-Story SMRF with 5 meters of debris load accumulation wrapping

Scour/Erosion – Plentiful ExamplesScour/Erosion – Plentiful Examples

8-ft. Scour by inflow at Dormitory Bldgcorner

8-ft. Scour by inflow at Dormitory Bldgcorner

Scour by return flow around MinamisanrikuApt. building corner

Scour by return flow around MinamisanrikuApt. building corner

Onagawa scour from return flow from valleys

Onagawa scour from return flow from valleys

Miyako Bridge Abutment Scour

Miyako Bridge Abutment Scour

Special Occupancy RequirementsSpecial Occupancy Requirements

Vertical Evacuation Refuge Structures Vertical Evacuation Refuge Structures

Summary of information in the paperSummary of information in the paper

A method of probabilistic tsunami hazard analysis has been established.

Methodologies for 2D tsunami inundation modeling have been further developed.

Structural loading and analysis techniques for determining building performance have been developed.

Analysis procedures for regions governed by local subduction earthquakes involves a multi-hazard performance-based approach

The proposed ASCE 7 provisions for Tsunami Loads and Effects enables a set of analysis and design methodologies that are consistent with tsunami physics and performance based engineering.

A method of probabilistic tsunami hazard analysis has been established.

Methodologies for 2D tsunami inundation modeling have been further developed.

Structural loading and analysis techniques for determining building performance have been developed.

Analysis procedures for regions governed by local subduction earthquakes involves a multi-hazard performance-based approach

The proposed ASCE 7 provisions for Tsunami Loads and Effects enables a set of analysis and design methodologies that are consistent with tsunami physics and performance based engineering.

The ASCE Tsunami Loads and Effects Subcommittee will meet again in February 2013: your suggestions are welcome

Questions to: Gary Chock, Chair gchock@martinchock.com

The ASCE Tsunami Loads and Effects Subcommittee will meet again in February 2013: your suggestions are welcome

Questions to: Gary Chock, Chair gchock@martinchock.com“Soliton Fission” broken waves are just the short period waves on top of the long period tsunami